Heart failure remains a leading cause of disability and mortality in the United States and other Western nations. Heart failure progressing to end-stage cardiomyopathy can develop among patients with ischemic heart disease secondary to significant coronary atherosclerosis. Patients with viral myocarditis or valvular disease also are at risk for developing significant cardiomyopathy. Cardiac transplantation, ultimately, is the therapy for end-stage cardiomyopathy, whether the etiology is ischemic or non-ischemic, if pharmacologic measures fail. Transplantation however is limited by the available supply of donor organs. Consequently, efforts have been directed towards developing safe, implantable and long-term means of mechanical support for the patient awaiting transplantation. FDA approval has been granted to several mechanical ventricular assist devices (VADs) with application as a “bridge-to-transplant.” Clinical studies demonstrate that implantation of such a device provides sufficient circulatory support to aid the patient's recovery from sequelae of end-stage cardiomyopathy such as renal and hepatic failure, and to allow physiologic rehabilitation until a donor heart is available. Cardiac arrhythmia is a significant complication of end-stage cardiomyopathy, with patients prone to developing either atrial fibrillation, resulting in an irregular rhythm with increased potential for stroke, or potentially fatal ventricular tachyarrythmias such as ventricular tachycardia or fibrillation. Cardiomyopathy patients can also develop bradyarrhythmia, or an abnormally slow heart rate. Treatment of these conduction disorders can require implantation of a permanent pacemaker, an automatic internal cardiac defibrillator or both.
As the clinical experience with implantable VADs has increased several investigators have observed a number of chronic heart failure patients who demonstrate not only recovery of end-organ damage and functional improvement, but also recovery of myocardial function following VAD implantation. These patients demonstrated recovery by several clinical parameters of myocardial function, including improved myocardial contractility or wall motion seen on serial echocardiography, increased exercise capacity greater than that expected from mechanical support alone, and the ability to maintain adequate cardiac output during periods of temporarily decreased VAD support. Only a few such patients have undergone VAD explantation and maintained native heart function sufficient to sustain life. However, it appears that long-term implantable mechanical ventricular assist devices can be applied in select patients not as a “bridge-to-transplant,” but as a “bridge-to-recovery.”
The present invention aims at providing a physician with means for natural heart restoration. In other words, to enlarge the class of patients for whom VAD explantation is to be made possible. Furthermore among this enlarged class, it is expected that after explantation, some patients will do far better than barely sustaining life, but will gradually be able to engage in normal activities with a completely restored native heart. In the present application, the terms “natural heart” and “native heart” mean one and the same heart of the patient.